Apple Pectin-Based Hydrogel Electrolyte for Energy Storage Applications

Demand for flexible energy storage devices is rapidly increasing due to the development of new wearable and flexible electronics. These developments require improved integration of energy storage devices to meet the design specifications of these products. Polymer hydrogels are an alternative class of flexible electrolytes that can be used in power source systems. Herein, we present a new sustainable hydrogel electrolyte material made with apple pectin. Using an easy solution casting approach, a bio-based hydrogel was formed via pectin gelation. The resultant hydrogel was made with environmentally benign compounds including water, zinc and/or lithium sulfate salt, and a bio-based polymer. This hydrogel electrolyte exhibits ambient temperature ionic conductivities that are similar to those found in aqueous liquid electrolytes (∼5 × 10–2 S cm–1), depending on electrolyte hydration. Its wide thermal stability window enables the electrolyte to be used at both low temperatures (−20 °C) and intermediate temperatures (50 °C), without significant changes in ionic conductivity (>10–3 S cm–1). By proposing an energy-oriented solution using one of the food industry’s major waste materials, we report a novel approach to processing a bio-based polymer for energy storage purposes.